Work vehicles such as a hydraulic excavator, a bulldozer, a wheel loader, and the like have an exhaust gas treatment device. For example, a diesel particulate filter device (DPF), a diesel oxidation catalyst device (DOC), a selective catalytic reduction device (SCR), and the like are available as exhaust gas treatment devices. Particularly, the selective catalytic reduction device reduces nitrogen oxide contained in an exhaust gas to purify the exhaust gas. A reducing agent used for this exhaust gas treatment is stored in a reducing agent tank.
When the reducing agent is frozen in the tank, the reducing agent cannot be supplied to the exhaust gas treatment device. Therefore, for the purpose of preventing freezing of the reducing agent in the reducing agent tank, the technique of arranging a heat exchanger in the reducing agent tank to heat the reducing agent has been proposed. For example, Japanese Patent Laying-Open No. 2010-71263 (PTD 1) discloses an aqueous urea solution tank in which a cooling water pipe through which engine cooling water flows for heating aqueous urea solution is configured to be suspended downward from a top cover which closes an opening of an upper face of a tank main body and bent in a periphery of a bottom portion of the tank main body, extend horizontally, and reach a turning portion.